近50 a高台县绿洲时空变化研究

以近50 a的13期KeyHole、KATE-200、LandsatMSS/TM影像为数据源，提取高台县绿洲分布情况。计算绿洲单一动态度、双向动态度以及各乡镇绿洲相对变化率，并对高台绿洲13期矢量数据做叠置分析，确定高台绿洲在时间序列上的面积和空间变化情况。结果表明：近50 a高台县绿洲主要以扩张为主，其中绿洲扩张最迅速的时期是1990-1993年；双向动态度分析结果表明，绿洲-非绿洲相互转化剧烈；稳定绿洲主要分布在黑河沿岸以及各乡镇居民区周围，变化绿洲分布在稳定绿洲外围，骆驼城乡、南华镇是绿洲扩张主要区域，绿洲频繁波动和退缩现象主要出现在罗城乡、新坝乡、黑泉乡一带。

Spatiotemporal Change of the Oasis in Gaotai County in Recent 50 Years

Distribution of the oasis in Gaotai County, Gansu Province was extracted by taking the 13 images in recent 50 years as the data sources, including LandsatMSS/TM, KeyHole and KATE-200. The single dynamic degree and bidirectional dynamic degree of the oasis were calculated, the relative change rates of the oasis in all the townships and towns in Gaotai County were estomated, and an overlay analysis on the vector data about distribution of the oasis in 13 periods were carried out to get the area and spatial change of the oasis in time sequence. The results showed that the oasis in Gaotai County was in expansion in recent 50 years, especially during the period from 1990 to 1993. The analyzed results of bidirectional dynamic degree revealed that the conversion between oasis and non oasis was violent. The stable parts of the oasis were mainly distributed along the Heihe River and around the residential areas, the changeable parts of the oasis were distributed surrounding the oasis. The urban and rural areas of Luotuo Town and Nanhua Town were the main areas where the oasis was in expansion, and the frequent expansion and shrinkage of the oasis occurred mainly in Luocheng, Xinba, Heiquan townships.